I mean he can't run after Lion, because Lion himself isn't able to run for now.
I think the way they showed her walking down the stairs, the effect it had on him, seeing her all dressed up and knowing what she's going to the Ds for, and then hearing Lion threaten to harm her, all of it combined ignited something in him.
He's going to be so protective of her after this. I have a feeling he will continue to hide Lion's arrival for a bit longer and in the meantime restrict her movements. She's bound to feel suffocated.
